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Abstract Torrefaction is a thermal pretreatment method to increase the energy density and to decrease the grinding energy of biomass. In this study, the torrefaction of two types of commercially available wood pellets was carried out in the temperature range of 230–290 °C for 30 min residence time. Torrefaction produces both the solid fuel known as torrefied pellets and the volatile stream known as torgas. The torgas was further separated into condensable liquids, known as tor-liquid and non-condensable gases. The products yield, its compositions and fuel properties at various torrefaction temperatures were also determined. The increase in temperature reduced the torrefied pellet yield from 89 to 52%, while increased the condensable liquid yield from 5 to 23% within the torrefaction study condition. The heating value (24 MJ kg−1) and the volumetric energy density (12.5 GJ m−3) of torrefied pellets at 270 °C were comparable to that of coal for biopower. The increase in torrefaction temperature improved the hydrophobicity (resistance to water uptake), but adversely reduced the pellet density, hardness, and durability of torrefied pellets causing high susceptibility to breakage and fine generation during handling, transport, and storage. Further research is required to improve the quality of torrefied pellets for safe handling and storage. The non-condensable fraction of torgas was mainly composed of carbon dioxide, carbon monoxide, and traces of methane. The condensable liquid was rich in organic acids, ketones, furfural, and levoglucosan, which could be potentially transformed into high-value chemicals and other commercially viable products. Highlights • Torrefied pellet yield reduced from 89 to 52% between 230 and 290 °C. • Torrefied pellets produced at 270 °C had similar fuel properties as coal. • TAP pathway improved the hydrophobicity of wood pellets. • Pellet hardness and durability decreased with increased torrefaction temperature. • Tor-liquid was rich in organic acids, and levoglucosan and can be a co-product. [ABSTRACT FROM AUTHOR]

The assessment of biomass at high spatial resolution is critical to manage supply risks and to identify optimal plant sites for producing sustainable biofuels and co-products. The spatial variabilities in soil type, topography, climate, and crop management practices further require vast computational time and resources to estimate the availability of sustainable biomass for a large study area. In this study, we developed a GIS-based integrated predictive modeling platform to assess the availability of sustainable crop residues at high spatial (30 m) and temporal (2010–2022) scales. A GIS-based multi-criteria inclusion-exclusion analysis and facility location-allocation models were used to identify suitable sites, and optimal siting of biogas plants respectively with biomass delivered cost. The Artificial Neural Network (ANN) based predictive models were well suited to predict sustainability indicators (soil erosion SE- R 2 = 0.96, soil conditioning index, SCI R 2 = 0.98 and organic matter factor, OMF- R 2 = 0.83) for assessing sustainable removal rates of crop residues (corn stover and wheat straw). The GIS-based integrated model was applied to the State of Ohio and found that about 4–13 dry Tg of crop residues can be sustainably available to build 1–25 regional biogas plants. A typical optimal biogas plant with a feedstock capacity of up to 500 dry Gg could be drawn from a transport radius of about 19–35 km with a delivered cost of 40–46 $ dry Mg −1 . The temporal and spatial variations in assessing the availability of biomass largely affected the supply chain decisions and its delivered costs. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical properties of wheat straw, barley straw, corn stover and switchgrass were determined at different compressive forces, particle sizes and moisture contents. Ground biomass samples were compressed with five levels of compressive forces (1000, 2000, 3000, 4000 and 4400N) and three levels of particle sizes (3.2, 1.6 and 0.8mm) at two levels of moisture contents (12% and 15% (wet basis)) to establish compression and relaxation data. Compressed sample dimensions and mass were measured to calculate pellet density. Corn stover produced the highest pellet density at low pressure during compression. Compressive force, particle size and moisture content significantly affected the pellet density of barley straw, corn stover and switchgrass. However, different particle sizes of wheat straw did not produce any significant difference on pellet density. The relaxation data were analyzed to determine the asymptotic modulus of biomass pellets. Barley straw had the highest asymptotic modulus among all biomass indicating that pellets made from barley straw were more rigid than those of other pellets. Asymptotic modulus increased linearly with an increase in compressive pressure. A simple linear model was developed to relate asymptotic modulus and maximum compressive pressure. [Copyright &y& Elsevier]

Wheat and barley straws, corn stover and switchgrass at two moisture contents were ground using a hammer mill with three different screen sizes (3.2, 1.6 and 0.8 mm). Energy required for grinding these materials was measured. Among the four materials, switchgrass had the highest specific energy consumption (27.6 kW h t-1), and corn stover had the least specific energy consumption (11.0 kW h t-1) at 3.2 mm screen size. Physical properties of grinds such as moisture content, geometric mean diameter of grind particles, particle size distribution, and bulk and particle densities were determined. Second- or third-order polynomial models were developed relating bulk and particle densities of grinds to geometric mean diameter within the range of 0.18–1.43 mm. Switchgrass had the highest calorific value and the lowest ash content among the biomass species tested. [Copyright &y& Elsevier]